! [rejected]        main -> main (non-fast-forward)
error: failed to push some refs to 'github.com:user/repo.git'
hint: Updates were rejected because the tip of your current branch is behind

Someone else pushed changes to the remote branch since your last pull. Git won’t let you overwrite their work.

Fix 1: Pull and Merge (Safest)

git pull origin main
# Resolve any merge conflicts if they appear
git push

Or with rebase for a cleaner history:

git pull --rebase origin main
git push

Fix 2: Force Push (Only If You Know What You’re Doing)

# Safe force push — checks that no one else pushed
git push --force-with-lease

# Dangerous force push — overwrites everything
git push --force

⚠️ Only force push on branches that only you use. Never force push main on a shared repo.

Fix 3: After a Rebase or Amend

If you rebased or amended a commit that was already pushed:

# This is expected after rebase/amend
git push --force-with-lease

--force-with-lease is safer than --force — it fails if someone else pushed in the meantime.

When This Happens

• You and a colleague both pushed to the same branch
• You rebased or amended a pushed commit
• You reset your local branch to an earlier commit
• CI/CD made a commit (like a version bump) that you don’t have locally

Prevention

• git pull --rebase before starting work each day
• Use feature branches instead of pushing directly to main
• Use --force-with-lease instead of --force when you must force push